@Joseph-TP 

Hi Joseph, thank you for your reply.

I've already followed all of the suggested steps:

1. ✅ I tested my router with a phone and achieved 850+ Mbps download speed — so the issue is clearly not on the router or connection.

2. ✅ My PC doesn’t have an internal Wi-Fi adapter. I’m using only the TP-Link Archer T3U Plus, connected via USB 3.0.

3. ✅ The PC is placed right next to the router, with excellent signal quality.

4. ✅ I’m connected to the 5 GHz band, specifically channel 36, which avoids DFS restrictions.

5. ✅ I’ve ensured clean, low-interference channel selection and high transmit power. WPA2-AES encryption is used.

📷 I’ve also attached a screenshot of my wireless configuration for clarity.

https://drive.google.com/file/d/1KXDWuPv9I69UqQC5vOYIqJbnoxw5DIjh/view?usp=sharing

https://drive.google.com/file/d/10no4v1asOsfuxoJYCVTUPzPgXpEH-i33/view?usp=sharing

You can see that:

• 5 GHz is enabled on channel 36

• I am connected via SSID6 (5GHz) as shown

Despite a link speed of 780 Mbps, the actual download speed remains stuck around 300 Mbps, even under ideal conditions.

From what I’ve gathered, the Archer T3U Plus appears to use a single antenna and 1x1 MIMO, which seems to realistically cap performance at around 300–350 Mbps.

So here’s my main question to the community:

👉 Has anyone ever reached 600–700+ Mbps real-world speed using this exact adapter (T3U Plus)?
I'm trying to confirm whether this is a common hardware limitation, or if there might be something wrong or misconfigured on my side.

Thanks again, and I appreciate any input from others who have tested this adapter.

Best regards.

  @delimiyimben 

Hi,

For this type of AC Wi-Fi adapter the theoretical limit with one antenna is 433 Mbps and with two antennas 867 Mbps.

A reasonable real-world speed for the T3U Plus would be around 450 Mbps, perhaps 600 Mbps are possible in optimal conditions.

One thing that USB AC Wi-Fi adapters based on Realtek chips have in common is that support for USB 3.0 mode is somewhat patchy.

I suggest you use a software like SIV System Information Viewer or USB Device Tree Viewer to find out whether the T3U Plus is currently running in USB 3.0 mode or in USB 2.0 mode. The latter would explain why the speed is being capped at 300 Mbps. (the "mode" I am talking about is independent of the port physically being USB 3.0)
 

  @woozle 

Hi, thanks for the answer.

I've been troubleshooting my TP-Link Archer T3U Plus adapter, and noticed it only connects as USB 2.1 (High-Speed) instead of USB 3.0 (SuperSpeed).

I verified this using USB Device Tree Viewer, which shows the device is SuperSpeed-capable but only operates at High-Speed.

To rule out port issues, I tested a USB 3.0 portable hard drive on the same ports-it correctly connects at USB 3.0 speed. So I’m assuming the issue lies with the adapter itself.

I also installed the latest Realtek driver, but it didn’t change anything.

Any ideas or known issues regarding this behavior?

  @delimiyimben 

Yes, this is a known issue. There have been plenty of threads about it in this forum.

Some users were able to solve it by trying various different versions of the driver, others by trying different USB 3 ports (because some computers have more than one USB 3 controller), yet some users still couldn't make it work.
 

  @delimiyimben 

This is exactly the kind of answer I was looking for. Thanks for sharing